Production of penta-2,4-dien-1-als and related trienals

ABSTRACT

Manufacture of penta-2,4-dien-1-als comprising the reaction of propargyl alcohols with Alpha -formylcarboxylic esters at temperatures of from 100* to 350* C. Penta-2,4-dien-1-als are odorants.

United States Patent Hoffman et al.

[ Feb. 18, 1975 1 PRODUCTION OF PENTA-2,4-DIEN-1-ALS AND RELATEDTRIENALS [75] Inventors: Werner Hoffmann, Ludwigshafen;

Walter Himmele, Walldorf; Werner Aquila, Ludwigshafen, all of Germany[73] Assignee: Basf Aktiengesellschaft,

Ludwigshafen/Rhein, Germany 221 Filed: Nov. 5, 1973 211 Appl.No.:412,733

Related US. Application Data [63] Continuation-impart of Ser. No.79,299, Oct. 8,

l970, abandoned.

[30] Foreign Application Priority Data Oct. 15, 1969 Germany l95l883[52] US. Cl. 260/601 R, 252/522, 260/602, 260/638 R, 426/22 [51] Int.Cl. C07c 47/20, C07c 47/26 [58] Field of Search 260/601 R, 602

[56] References Cited OTHER PUBLICATIONS Beilsteins Handbuck der OrganChemie" Band I, Hauptwerk, pp. 757-758 (1918). J. L. Simonsen, TheTerpenes", Vol. I, p. 88 (1953).

Primary Examinerloseph E. Evans Assistant ExaminerD. B. SpringerAttorney, Agent, or Firm.lohnston, Keil, Thompson & Shurtleff 6 Claims,No Drawings PRODUCTION OF PENTA-2,4-DIEN-l-ALS AND RELATED TRIENALS Thisapplication is a continuation in part of application Ser. No. 79,299filed Oct. 8, 1970, and now abandoned.

The invention relates to a process for the manufacture ofpenta-2,4-dienl -als by reacting substituted propargyl alcohols witha-formylcarboxylic esters.

it is an object of the invention to provide a process which produces alarge number of penta-2,4-dien-l-als not hitherto available. It isanother object of the invention to provide a process which produces goodyields.

In accordance with the present invention these and other objects andadvantageous are achieved in a process for the manufacture ofpenta-2,4-dien-1-als of the general formula:

in which R and R have the meanings given above, with a-formylcarboxylicesters of the general formula:

a 4 ao ccno In in which R" has the meaning stated above and R stands foralkyl of from one to four carbon atoms at temperatures ranging from 100to 350 C and from 1 to 5 moles of a-formyl carboxylic esters beingapplied per mole of said propargyl alcohols.

Preferred starting materials of formula II are those in which R standsfor a hydrogen atom or a methyl radical, R stands for4-methylpent-4-en-1-yl, 4-methy1-4- methoxypent-l-yl, 4-methy1pent-l-yl,4,8-dimethylnona-3,7-dien-l-yl or 2-ethylpent-l-yl. Examples of suitablestarting materials are: 3,7-dimethyloct-7-en-lyn-3-ol;7-methoxy-3,7-dimethyloct-l-yn-3-ol; 3,7- dimethyloet-o-en-1-yn-3-o1;dehydronerolidol; 4-ethyloet-1-yn-3-ol; dehydroisophytol; 3-methylpent-1-yn-3-ol or 3-methylbut-1-yn-3-ol.

1n the preferred starting materials of formula III, R stands for alkylof from one to four carbon atoms. and R stands for alkyl of from one tofour carbon atoms. Suitable starting materials are, for example,methyl-a-formylpropionate, n-butyl a-formylpropionate, methyla-formylbutyrate and n-butyl a-formylbutyrate.

It is advantageous to use from 1 to 5 moles of starting material offormula 111 per mole of starting material of formula 11. Particularlygood results are obtained when from 1.2 to 2.5 moles of startingmaterial of formula III are used per mole of starting material offormula 11.

The reaction is carried out at temperatures ranging from to 350 C.Temperatures of from to 220 C are particularly beneficial. The reactionis generally carried out at atmospheric pressure, but it is possible touse pressures of from 100 mm of Hg to 10 atmospheres.

In general no solvents are used in carrying out the reaction. However,solvents and diluents may be used if desired, for example inerthigh-boiling hydrocarbons such as perhydro and tetrahydro naphthalene,dimethyl formamide and N-me'thyl pyrrolidone.

The process of the invention is carried out, for example, by placing thestarting materialsof formulae l1 and [11 in the desired proportions,optionally together with solvents, in a reaction vessel and heating tothe temperatures specified. Since alcohol and carbon dioxide areeliminated during the reaction, it is easy to determine the conclusionof the reaction. After the removal of any solvents the reaction mixtureis worked up by known methods, for example, by fractional distillation.Unconverted starting materials may be recycled to the reaction. Thereaction may be-carried out continuously by simple means.

The compounds prepared by the process of the invention are odorants.They are distinguished particularly by a fruity odor and taste;2,5,9-trimethyldeca- 2,4,9-trien-l-al, for example, has a pronouncedorange odor and taste and is used-in the beverage industry for makingappropriate fruit drinks.

The process of the invention is illustrated in the following Examples.

EXAMPLE 1 A mixture of 76 g of 3,7-dimethyloct-7-en-lyn-3-ol and 87 g ofmethyl a-formylpropionate is heated at 160 C. The methanol eliminated iscontinuously distilled off via a column. During the reaction thetemperature is raised to 200 C. The reaction is complete after about 3hours. The resulting reaction mixture is worked up by fractionaldistillation. There are thus obtained 71 gof2,5,9-trimethyldeca-2,4,9-trien-l-al (76% of theory), b.p. 98-99 C/0.01mm, refractive index n 1.5299. The product has a distinctly fruity odorresembling that of raspberries.

EXAMPLE 2 EXAMPLE 3 A mixture of 77 g of 3,7-dimethyl-oet-1-yn-3-ol and87 g of methyl a-formylpropionate is heated as in Example for 3 hours attemperatures ranging from C to 210 C. After fractional distillation ofthe reaction mixture there are obtained 69 g of 2,5,9-trimethy1deca-2,4-dien-l-al (73% oftheory), b.p. 7881C/O.18 mm, refractive index 111.5132.

EXAMPLE 4 A mixture of 110 g of dehydronerolidol and 87 g of methyla-formylpropionate is heated as in Example 1 for 2 hours at from 180 to200 C. After fractional distillation of the reaction mixture there is ayield of 63% o12.5.9.13-tetramethyltetradcca-IZ,4,8,l l-tctraen- 1 -al,b.p. 125127 (70.02 mm. refractive index 1.5190.

EXAMPLE A mixture of 77 g of 4-ethyloct-1-yn-3-ol and 87 g of methyla-formylpropionate is heated for 5 hours at temperatures ranging from145 to 220 C. After fractional distillation of the reaction mixturethere is obtained a yield of 68% of 6-ethy1-2-methyldeca-2,4-dienl-al,b.p. 74-78 C/0.2 mm, referactive index n,, 1.5148.

We claim:

l. A process for the manufacture ofa penta-2,4-dien- [-211 of theformula in which R stands for hydrogen or methyl, R stands for analiphatic hydrocarbon radical of one to nine carbon atoms, which radicalmay contain one or two olefinically unsaturated double bonds and whichmay bear from one to three substituents selected from the groupconsisting of methyl. ethyl and methoxy and in which R" stands for alkylof one to four carbon atoms. which process comprises: contacting apropargyl alcohol of the formula I 110-; ;ca (II in which R and R havethe meanings given above,

with an a-formylcarboxylic ester of the formula 0 H n I R -OC-?5CHO (IIIin which R has the meaning given above and R stands for alkyl of one tofour carbon atoms. at a temperature of from to 350 C. and from 1 to 5moles of an a-formyl carboxylic ester are used per mole of saidpropargyl alcohol.

2. 2,5,9-Trimethyldeca-2,4,9-trien-l-al.

3. A process as claimed in claim 1 wherein the starting material is apropargyl alcohol of the formula per mole of the propargyl alcohol.

1. A PROCESS FOR THE MANUFACTURE OF A PENTA-2,4-DIEN-1-AL OF THE FORMULA3. A process as claimed in claim 1 wherein the starting material is apropargyl alcohol of the formula
 4. A process as claimed in claim 1wherein methyl Alpha -formylpropionate is used.
 5. A process as claimedin claim 1 wherein a temperature of from 120* to 220* C is used.
 6. Aprocess as claimed in claim 1 wherein from 1.2 to 2.5 moles of an Alpha-formylcarboxylic ester are used per mole of the propargyl alcohol.